Apart from the occasional misguided instruction, sat-nav has so far proved an extremely popular device with British motorists.

But today it emerged that the same technology is being used to develop a new generation of sophisticated speed cameras.

Combining number plate recognition technology with global positioning satellite (GPS), the machines will be able to secretly follow a driver’s progress over a distance of several miles between camera points, measuring the average speed.

Known as SpeedSpike, the system uses similar methods of recognition as the cameras which enforce the congestion charge in London, and allow two cameras to ‘talk’ to each other if a vehicle appears to have travelled too far in too short a space of time.